Control system for electric motors .



H. D. JAMES. CONTROL SYSTEM FOR ELEGTRIG MOTORS.

APPLIOATION FILED 0011 3, 1906.

Patented June 15, 1909.

WITNESSES Unrrnn sTATEs racism OFFICE.

HENRY D. JAMES, OF PITTSBURG, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSEELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

CONTROL SYSTEM FOR ELECTRIC MOTORS.

' of the motors are governed byadjustin the them'with ener y. l

field excitation of the generators supp ying The object o my inventionis to provide means whereby the operation of systems of the characterindicated may be improved and be rendered more reliable thanhasheretofore been the case, and whereby the motors and other devices inthe system may be pro tected from injuries resulting from abnormalconditions. 7

When electric motors are employed to operate large variable -'loads,they are frequently governed as totheir speed and direction of rotationby adjusting the field strengths} and polarities of the generators.supply'ing them with energy, and further variations in speed are often'eflected by means of rheostats in .the field circuits ofthe motors.

According to the present invention, too rapid acceleration in the speedofthe motor is prevented by preventing movement of the motor fieldrheostat from its initial position until the generator field hasbeenstrengthened to a predetermined value, and also until the motor hasattained a predetermined pied .Movement' of the generator field rstatis'l prevented after the motor been moved fromjtsdnitgia'l position.

The. invention further provides means for interrupting the field circuitof the enerator when t e current in the motorfiel winding falls below apredetermined amount; when the spedd of the motor exceeds a predeter;

mined value, and when the currentsupplied by the generator to the motorexceeds a predetermined amount. i

The single figure of the accompanying, drawing is a, diagrammatic viewof a contro system thatembodies my invention.

, The rotatable members 1 and 2 of motors 3 v Specification of LettersPatent.

Application filed October 3, 1906. Serial No. 337,280.

Patented June 15, 1909.

1 and 4 are mechanically connected together andmay be also mechanicallyconnected to a variable load, such as hoisting machinery or a rollingmill. The members 1 and 2 are supplied With current from a directcurrent generator 5 having two commutators 6 and 7 to which the resective members 1 and 2 of the motors are e ectrically connected. The ar;mature of the generator 5 is driven by means of an alternating currentinduction motor 8 that also drives a heavy fly-wheel 9, the rimarymember of the motor being supp ied with current from any suitable sourceor cir- 11 and 12. The s eed of the motor 8 is governed automatical y bymeans of a plurality of separately. actuated switches 13, 14, 15, 16 and17, whereby the amounts of resistances 18, 19 and 20, that are includedin circuit with the secondary member of the motor, maybe adjusted- Theswitches 13 to 17, inclusive, are provided with operating or controllingmagnet windings 21, 22, 23, 24 and 25, the circuits of which arecontrolled by interlocking switches 26, 27, 28, 29 and 30, and tworelaysWitches 31 .and 32, the movable members of said interlockingswitches being so connected to the corresponding movable m'e'mbers ofthe switches 13 to 17 as to be actuated with them. The relay switches 31and 32 are provided With operating magnet windings 33 and. 34,respectlvely, that are supplied with current from switches 31 and 32 areso adjusted that the switches 13110 17 inclusive, will be operated toinsert resistance in or remove it from the secondary circuit of themotor 8 according as the'load rovided b the generator 5 exceeds or fallselow pre etermined amounts, the speed of the motor bein allowed todecrease when the generator 10a exceeds a predator mined value, so thatthe kinetic energy of the ,isconne'cted to the istributing circuit. The

cuit, such. as that comprising conductors 10,

an auto-transformer winding 35,;the active light the motor 8 mayincrease in speed and cause energy to be stored in the fly-wheel-9.

' In this manner, the amount of current derived from the distributingcircuit 10 -1 1-l2 may be maintained substantially constant andprevented from' exceeding a predetermined value, the details of theoperation of this portionof the system being here mentioned only brieflybecause the same are fully set forth in a separate application, SerialNo. 337,278, filed by me of even date herewith.

The respective terminals 43 and 44 of the field magnet winding of thegenerator 5 are connected to the middle or other normally equi-potential)oints of two sub-divided resistances 45 and 46 that are connected inparallel relation to a direct current distributing circuit, comprisingconductors 47 and 48, by means of a circuit-breaker 49. The severalpoints of sub-division of the resistances 45 and 46 are connected to aplurality of stationary contact terminals 50 of a controller 51, thecontact terminals being arranged in four groups 52, 53, 54 and 55 withwhich brushes 56, 57, 58 and 59, upon the extremities of a-fourar1nedmovable member are adapted to engage. 'l he brushes 56 and 57 areconnected by meansof a conductor 61,- and the brushes 58 and 59 aresimilarly connected by means of a conductor 62, and the directionandvalue of the drop of potential in the field magnet winding of thegenerator 5 may be adjusted by rotating the movable bracket 60 to theright or to the left the desired amount. In this manner, the polarityand field strength of the generator may be adjusted to control thedirection and value of the voltageappli'ed by the generator to themembers 1 and 2 of the motors and thus effeet adjustment of thedirection of rotation and speed of operation of the motors. Thecontrollenhere shown and described forms the subject-matter of anotherapplication, Serial No. 337,279, filed of even date herewith, and it isconsequently deemed unnecessary to set forth more in detail itsstructure and mode of operation.

Adjustment of the s eed of the motors may be further? effected y meansof a rheostatic controller 65 that is connected between the field magnetwindings of both of the motors and thejdistributing circuit conductors47 and 48. The controller 65 comprises a four-armed member 66 and itsmechanical structure is otherwise similar to that of the controller 51,though the arrangement and connections of the resistances aresubstantially as set forth in Patent No. 610,124, granted toWestinghouse Electric & Manufacturing Company, as assignee of Harry P.Davis.

Permanent adjustment of the speed characteristics of the motors 3 and 4may be effected by means of an auxiliary resistance 67, and the motors 3and 4 may be caused to opcrate atexactly the same speed and undersimilar conditions by means of a comparatively high resistance 68 thatis connected in parallel relation thereto, and an intermediate point 69of which is'connected to terminals of the field magnet windings of themotors.

The movable members 60 and 66 of controllers 51 and 65 are connected,respectively, by means of rods 70 and 71 to sectorshaped cams72 and 73,the former of which is provided with notches 74 and 75 neartheextremities of its arc-shaped edge, and the latter-of which is providedwith a notch 76 at approximately the middle of its arc-shape edge. A bar77 is pivoted intermediate t e cams 72 and 73 and is provided at itsextremities with projections that are adapted to fit into the notches inthe cams, the parts being so proportioned and arranged that when theprojection at one end of the bar engages the arc-shaped edge of thecorresponding cam, the projection at the other end of the bar is locatedin a notch in the other cam and thereby prevents movement of the cam andof. the corresponding controller bracket.

Thus, when the member-60 of the generator field rheostat 51 occupies thepositiolfsh'own,

i. 1 when the field magnet winding 'of the generator is not excited,movement of'the member 66 of the motor field rheostat 65 is prevented.When the member 60 is moved to one of its extreme positions, however,the projection 78 may engage the one or the other of the two notches 74and 75, and the projection 79 may thus be raised-out of the notch 76 inthe cam 73 by movement of the member 66 of the controller 65. Suchmovement, however, will be prevented by an electro-magnetically operatedlatch 80, until the motors 3 and 4 attain a predetermined speed, saidlatch having a winding 81,

the circuit of which is controlled by means of a switch 82. T he switch82 is provided with an operating magnet winding 33 that is connected toa small magneto-dynamo 84, and becomes sufiiciently energized to closethe switch and establish the circuit of the magnet winding 81 only whenthe voltage of the dynamo 84 exceeds a-predeterrnined value, i. e., whenthe motors have attained a predetermined speed. The latch 80 is thenwithdrawn and free operation of the bar 77 is permitted.

Included in series circuit with the field magnet windings of the motors3 and 4 is a magnet winding 85 that maintains a latch 86 in engagementwith a stop 87 a1ui.th.ereby whereupon the latch 86 drops out ofengagement with the stop 87 and permits the circuit breaker 49 to open.The respective terminals of the magnet winding are connected tostationary contact terminals 88 and 89 of a switch 90 having'anoperating magnet winding 91, the circuit of which becomes establishedonly when the speed of the motors 8 and 4 exceeds such a value that.

mo able members 92 of the one or the other of apair of centrifugalswitches 93, with;

which the rotatable members of the motors are provided, is caused toengage a stationary contact terminal94. The magnet winding 85 istherebyshunted and the circuit" v breaker 49 is permitted to open.

. A-pair of switches 96 and 97, that have opcrating magnet windings 98and 99 con nected in series, respectively, with the vconductors by meansof which currentis supplied to the motors-3 and 4, are employed forestablishing the circuit of the magnet windmg 91, when the currentsupplied by the generator to the motors exceeds a predetermined amount,the circuit-breaker 49 being there-- by caused to open.

The auxiliary or control circuits ofthe system are supplied from abattery 100, to

which they may be connected by means of a no-voltage relay switch 101having an operati'ng magnet winding 102 that is supplied from thesecondary Winding 103 of a transformer; 104, the primary winding 105 Iof which is connected between two of the conductors byineans of whichcurrent is supliedto the primary member of the motor 8. hus the controlcircuits may become established only when the, voltage applied to themotor 8 exceeds a predetermined value.

The specific devices which have here been shownand described are onlyillustrative of suitable means for, effecting the results set forth, andother means may obviously be devised and employed without altering themode of operation of the invention or departing from its spirit, and Idesire that all such modifications shall be included within its scape. 49 claim as my invention: 1. The comb nation with a generator and a motorhaving their armatures electrically connected together, ofresistance-varying devices for the circuits of the respective fieldmagnet windings of said machines, and

means ior preventing operation of the device means for preventingmovement of the device mthe motor field circuit from its initialposition until the device in the field'circuit oi the generator has beenoperated to its extreme position. .v 31 The combination with a generatorand a motor having their armatures electrically connected together, ofresistance-varying devices for the circuits of the respective fieldmagnet windings of said machines, means for preventing movement of thedevice in the motor field circuit from, its initial position until thedevice in the field circuit of the gcn' erator-has been operated to itsextreme position, and means for thereafter preventing operation of thelatter device unless the former occupies its initial position.

l. The combination with a generator and a motor having their armatureselectrically connected together, of resistance-varying devices for thecircuits of the respective field magnet windings of said machines, andmeans for preventing movement of the device in the motor field circuitfrom its initial position until the device in the field circuit of thegenerator has been operated-to its extreme position and until the motorhas attained a predetermined speed.- i

5. The combination witha generator and a motor having their arinatureselectrically connected together, of resistances for the circuit of therespective field magnet windings of said machines, means for varying thesame, and means for preventing variations of the resistance in the motorfield circuit until the resistance in the generator field circuit hasbeen adjusted to obtain a predetermined field strength.

6. The combination with a generator and a motor having their armatureselectrically connected together, of resistances for the circuits of therespective field magnet windings of said machines, means for varying thesame, and'means for preventing variations of the resistance in the motorfield circuit until the resistance in the generator field circuit hasbeen adjusted to obtain a predetermined eld strength'and until the motorhas attained a predetermined speed.

7. The combination with. a generator and a motor having their armatureselectrically field strength, and means for preventing variations of theresistance in the generator 'field circuit after the resistance in themotor field circuit has been changed from its initial value. v

The combination with a generator and aanotor having their armatureselectrically connected together, of means for interrupting the circuitof the field magnet winding of the a motor having their armatureselectrically connected together, of means for interrupting the circuitof the field magnet winding of the generator when the speed of the motorexceeds a predetermined value.

10. The combination with a generator and a motor having their armatureselectrically connected together, and means for interrupting the circuitof the field magnet winding of the generator when the current suppliedto the motor by the generator exceeds a predetermined amount.

11. The combination with a generator and a motor having their armatureselectrically connected-together, of regulating devices for varying thestrengths of the fields of the respective machines, and means forpreventing operation of the motor field-regulating device until theother regulating device has been operated to strengthen the generatorfield.

12. The combination with a generator and a motor having their arinatureselectrically connected together, of strength-regulating devices for thefields of sa.id machines,and means for preventing movement of the motorfield device from its initial position until the generator field devicehas been moved to its extreme posit-ion.

13. The combination with a generator and a motor having their armaturesdirectly coupled together electrically, of strengthregulating devicesfor the fields of said machines, and means for so interlocking saiddevices that neither olthem can be operated unless the other is in apredetermined position which will insuresafe and satisfactory operationof both machines.

In testimonywhereof, I have hereunto subscribed my name this 28th (1 a yof September, 1906.

' HENRY D. JAMES.

Witnesses EDWIN LEnR,

BIRNEY Hines.

